Considering Casting Simple Grey Iron Prism Shapes for Dovetail References. - Page 2
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  1. #21
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    Interesting idea, Richard. Thank you! I guess I envisioned what you are suggesting as an 18" long 45-60-75 triangle with maybe 2" faces and perhaps 3/8" thick sides. I think such a SE would weigh about 10 pounds. Maybe you were thinking equilateral which would also not present any special problems for my foundry. I will not be at the foundry for a week or so, but making a test pour in ten to 14 days is not out of the question. Making a core should be pretty straight forward and the pattern itself is also pretty simple. I never know for sure how a pattern will cast until I give it an actual try, but I don't foresee any problems with such a design.

    Denis

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    image.jpg

    These were the Moore-ish (apologies to the Spanish) type SE's I was thinking of. Don't think I've seen a triangle section like these.

    L7

    (And no, these wouldn't be cast from a 'simple' pattern!)

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    Quote Originally Posted by lucky7 View Post
    image.jpg

    These were the Moore-ish (apologies to the Spanish) type SE's I was thinking of. Don't think I've seen a triangle section like these.

    L7

    (And no, these wouldn't be cast from a 'simple' pattern!)
    Simple-no. Lots of identical cores stacked one on top of the other. Perfecting the relative sizes of the core arms and getting it to pour right likely took a fair bit of trial and some error. Nicely done. But modern car engines and transmissions and the like are far more complex and yet produced by the millions with amazing quality and accurate rendition of detail. Helps to have a huge budget, powerful pour-simulation software, and centuries of cumulative experience in your favor.

    The more I think about it the more I favor the 45-60-75 geometry. But I am still interested in what Richard saw and found useful.

    Denis

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    I have started on the pattern for a 45/60/75 hollow 18" prism that will be relatively thin walled but will have internal ribs (not hard to do with a properly designed core) grey iron prism. It will have provision for attachment of handles to the ends and the potential for the user to mill off flats and attach handles to the likely-little-used 75 degree angle as well. The 75 degree apex handles probably won't be often desired I suppose, but might as well think of them now.

    I should be able to test cast it by the end of next week.

    Denis

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    I have the pattern nearly completely done and the corebox is 60% done. Shooting to pour hot metal on or, hopefully, before the weekend. I will have to make a special flask for this particular pattern type, but that is only a 1-2 hour job. I was gone on a bicycling trip the latter part of last week so not much got done except for mulling over the best approach for molding the pattern and designing the corebox. Every pattern has its own special challenges and this one is unusual for the large length vs width of the core. It feels good to be making sawdust which I hope equates to making progress. That is usually but not always the case. ;-)

    Denis

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    Denis- I probably missed it, but the 18” combo prism/level in post #14- is that something that you routinely sell? Is it 100% finished. How could I contact you about getting one. Is there a viewing slot machined thru the angled face so that you can see it from the top(ish)?


    Sent from my iPhone using Tapatalk Pro

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    A really cheap way to make a prism straight edge is to buy a 72" pre-cast square piece of Dura Bar and have them cut it Diagonally corner to corner. When I had my machine shop, that's what I did and all I did was set them in Magnetic V blocks and grind them. It was under $200.00 for the 72" long or 2 of them. You could call Dur-a-bar Phone: (888) 387-2227 and ask them. Durabar say no heat treating is needed.

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    Quote Originally Posted by ripperj View Post
    Denis- I probably missed it, but the 18” combo prism/level in post #14- is that something that you routinely sell? Is it 100% finished. How could I contact you about getting one. Is there a viewing slot machined thru the angled face so that you can see it from the top(ish)?


    Sent from my iPhone using Tapatalk Pro
    Yes, the vial is visible from the top(ish). I just went out and took a look and you can see most of the width and all of the length of the vial it to about 70 degrees. If, for some reason it were essential to be able to see the vial from directly 90 degrees above the SE, it would be an easy matter to mill a viewing port in the top rail say 1/4” or 3/8” wide and maybe an inch long. There would be no harm to the S.E./prism/parallel in doing so. I could easily provide the tool with such a slot if desired by the buyer. Another simple solution would be to use a chunk of modeling clay to mount a little mirror strategically so the the vial could be seen from above or one could clip on one of those 1” oval bicycling mirrors like I use on my bike helmet.

    I am always interested in ideas on how to improve my products or make new ones. That’s the reason, fun, and challenge of making these tools. I don’t want to drive “my father’s Buick” (it was great for its time, of course) and I don’t think today’s scrapers should be relegated to it either.

    If you are interested in purchasing a SE, just contact me at Denis*g*foster. At. g*mail. &*com. Just leave out all the spaces and stars etc. And please note, my first name has just one “n”. (Some folks have trouble paying attention to detail, evidently, and keep on writing my name with 2 n’s on this forum.) PM’s also work, but my box fills up quickly and it is clunky.

    I sell raw, thermally stress relieved castings, as well as thermally stress relieved machined castings with and without provision for the vial. I can usually get the surfaces to within 2 thousandths flatness when machining. I have casting in stock stress relieved and ready for shipment and or machining and shipment. 18” SE’s fit, by design, in a USPS flat rate box making shipping quite economical

    Denis

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    I find weight limits my ability to feel proper hinging on a dovetail and enjoy using lighter tools. I really didn't need a Foster 18" prism given I have other straight edges, but am finding his prism hinges dovetails very nicely. I hear what you're saying, Richard, about using durabar and agree it's easy to machine and cheap, but I think after using it, Denis's 18" prism is just better. Just my non pro opinion. I'd be interested in the opinion of a pro scraper, like you Richard, if you get the chance to use Denis's prism.

    L7

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    Quote Originally Posted by Richard King View Post
    A really cheap way to make a prism straight edge is to buy a 72" pre-cast square piece of Dura Bar and have them cut it Diagonally corner to corner. When I had my machine shop, that's what I did and all I did was set them in Magnetic V blocks and grind them. It was under $200.00 for the 72" long or 2 of them. You could call Dur-a-bar Phone: (888) 387-2227 and ask them. Durabar say no heat treating is needed.
    I just got a quote from Durabar for a 72” 2.25x2.25” chunk of class 40 (they call it GS imported) stock. It was a few cents more than 340 dollars delivered to me in Bellingham. I suspect there may be cheaper ways to get smaller quantities of cast iron.

    But, really, I am not aimed at selling cheap raw material—-I’ll leave that to the “off-shore” folks. I am sure there are plenty of people who would want to buy raw stock, cut it up, stress relieve it, mill it, and then start scraping. I am selling a a semi-finished tool that is ready to scrape when you open the box and is lighter in weight and just as (actually more) rigid compared to a solid hunk of iron. So, for those who are so inclined, by all means buy bar stock. For those who want to buy a purpose-made semi-finished, nicely designed tool, buy one of my simple prisms or the more elegant combo prism/SE/level/parallel available nowhere else.

    I have not yet set the price for my triangular hollow 18” prism (an idea I got from Richard who said he had for decades wanted one—-thanks, Richard!) but it will be less than a third the cost of the raw material quoted above.

    Denis

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    Quote Originally Posted by dgfoster View Post
    18” SE’s ^^^ and the seriously well designed and crafted protective wooden case around them ^^^ fit, by design, in a USPS flat rate box making shipping quite economical ^^ and safe ^^^

    Denis
    There. Fixed that for yah.

    Lovingly crafted SE's.

    Lovingly crafted protection against shipping damage.

    Go for it. I did.


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    OT:
    There was a PM member from mid Michigan casting mill hold downs and the like.
    I wonder if anyone remembers his name or contact. I am thinking about a new design SG dresser that would be about as big as a cell flip phone. What would be the easy /low cost method of casting such a part.
    What method, sand cast/ lost wax/ other? Cast steel or cast iron? It would be a low stress part.

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    I also just called Dura-Bar and left a message asking about buying a 3 x 3 x 72 cut diagonally for a quote sheet that I will cut and paste here. I also asked in the message where it is cast.

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    Quote Originally Posted by michiganbuck View Post
    OT:
    There was a PM member from mid Michigan casting mill hold downs and the like.
    I wonder if anyone remembers his name or contact. I am thinking about a new design SG dresser that would be about as big as a cell flip phone. What would be the easy /low cost method of casting such a part.
    What method, sand cast/ lost wax/ other? Cast steel or cast iron? It would be a low stress part.
    Yes, and no sooner does it hit the public eye than somebody in Vietnam or India could start knocking it off, too, yah? See vee blocks and 1-2-3 blocks, spin indexers, etc.

    Casting is easier where environmental and safety rules are poor or non-existent as well as labour being cheap and/or desperate.

    You want to keep anything that SMALL and easy to ship by ignorant postal packet "US-made", might be better to machine the bugger from the solid such that it at least wants a Chinee CNC investment and coding time cost to match your work!

    SE's & dovetails - by comparison - are a "special case", far more about stability in larger sizes and the reputation of the maker for that than about cost.

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    The price has gone up for the Dura Bar. Had to have been over 10 yrs ago.

    Here is what I got today. I use to call those the big size and approx 4" diagonal x 3 on other sides, Smaller sizes would be cheaper. If anyone wants something let me know and I will order it and I have a Horz. band saw and can cut them to the length you need. It costs about $48.25 per foot my cost. I would want to make $20.00 per foot to hassle with it. So you would pay me $68.25 per foot plus UPS charge. Dura bar told me the bar was continuous cast in WoodStock IL.

    1 3.250"H X 3.250"W X 72.000"L 1 203.2 lbs 203 $579.522/EA $579.52
    GRAYIRON G2 IRON CUT PLATE
    OFFERING 3.250" SQUARE CUT PLATE
    CUT DIAGNALLY CORNER TO CORNER

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    I will be pricing my purpose-made hollow internally-ribbed cast iron 45-60-72 degree 18” prism thermally stress relieved at 90 dollars (60 dollars per foot). Machining of the surfaces will be available at something like 80 dollars and will ordinarily be within 2 thou of flatness. (I made nice fixture for my combo prism/SE/parallel/Ievel that will work nicely for these tools as well.) I expect to be ready to ship them next week in a USPS flat rate box to destinations in the US and Canada. Other shipping arrangements outside the US and Canada can be made. I’ll be posting pics of casting when they are available.

    Best to contact me via email
    Denis
    *g*
    Foster
    att
    G***mail*
    dottt
    cccommm

    Just leave out the spaces and stars and obvious misspellings used as robot deterrents.

    I am having fun right now gluing in the rib bars in the corebox.

    Denis

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    Dura- bar has gone way up since I last ordered some three years ago. By weight your quote, Richard, is 50% higher than the iron I bought. Maybe some of that is a cut charge. Maybe some is the current tarrif battle. Perhaps also end of an economic cycle market giddiness.

    Must be a good sized machine you're scraping if you need a 4" diagonal.

    L7

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    Quote Originally Posted by lucky7 View Post
    Dura- bar has gone way up since I last ordered some three years ago. By weight your quote, Richard, is 50% higher than the iron I bought. Maybe some of that is a cut charge. Maybe some is the current tarrif battle. Perhaps also end of an economic cycle market giddiness.

    Must be a good sized machine you're scraping if you need a 4" diagonal.

    L7
    I also got a formal raw material Durabar quote I mentioned the other day. It was for 2.25 square material 72” long. Notably it is GS grade which the salesman advised me was “imported.” G2 grade (reportedly made in USA) is not available in smaller sizes and may be the reason for the remarkably large(for a day-to-day prism) quote from Rich as that


    bf567d8a-7295-4539-946e-700e64722701.jpg
    may be the lower limit for domestic Durabar. For transparency and clarity I attached a copy of the quote not an excerpt. I highlighted the GS portion of the quote. Sorry about the crappy formatting of the quote. The software seems to struggle with copies of PDF’s.

    Looking forward to casting my first triangle prism (“Made in USA”. ;-) ) soon.

    Denis

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    Stan L7 I just requested a Dura-Bar quote for a 2" x 2 x 72 to see how much a smaller one would cost. It is so simple to buy Dura-Bar and grind it on a surface grinder before scraping them. I will cut and paste that price when I get them.

    I have made short ones during the class from the practice bars we use when learning. I can check with Starrett True-Stone Granite in St.Cloud MN. and see what the will charge for a granite prism. I have had Granite SE's made for customers. The one I show is at NSK in Indianapolis where I taught them to rebuild bearing grinders.

    They wanted Granite so they didn't need to rescrape cast iron. Plus Granite can be calibrated by sending it back to Tru-stone for ISO. Many times inspection departments won't calibrate Cast iron SE's. The other photo's she the cast bars we cut to make the small prism. Jan S from Norway took a GA class where we cut a bar and he scraped it. The one photo is me scraping a Swiss Screw machine slide I helped rebuild where we used Dura-Bar SE made from the test bars. We used the SE Jan is holding. Plus the HKA-18 SE I sell that works super on dovetails.
    Attached Thumbnails Attached Thumbnails 3177.jpg   dsc01935.jpg   dsc01914.jpg   2013-12-05_08-36-33_469.jpg   dsc02202.jpg  



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